An overview of recent advances on wheat homologous and homoeologous recombination

Crop breeding relies on the creation of highly performing varieties that possess a genotype containing numerous agronomical traits of interest. The specific combination of traits is generated in the parents by meiotic recombination, a highly conserved and controlled cellular process. Improvement of recombination, both in terms of quantity and localisation, would enhance the breeding capacities for all crops. This includes allopolyploid wheats (tetraploid durum wheat, Triticum turgidum ssp. durum, AABB genome; hexaploid bread wheat, Triticum aestivum, AABBDD), two of the most important cultivated species on the planet. As allopolyploid species, recombination in wheat is subjected to two levels of control: (1) recombination between homologous chromosomes that is favoured but has low frequency and uneven distribution; (2) recombination between homoeologous chromosomes that is prevented while this allows the introduction of diversity from related species. During the last ten years, a lot of effort has been conducted to identify and study genes involved in controlling the rate and distribution of homologous and homoeologous recombination in wheat. In this review, we focus on recent results and propose a model for the control of these two processes.